Authors: L.F. Chen, S.P. Ramirez Sebastian, J.A. Wang
Affilation: Instituto Politecnico Nacional, Mexico
Pages: 479 - 482
Keywords: hydroisomerization, n-hepatne
The present work aims at searching for new catalysts for n-heptane isomerization. Four WO3-ZrO2 oxides were prepared by varying WO3 content in 5, 10, 15 and 25 wt% using a sol-gel technique. The 1wt% Pd/WO3-ZrO2 catalysts were prepared by impregnating PdCl2 aqueous solution on the support. The crystalline structure, acidity, reducibility and morphological features were studied by XRD, FTIR, H2-TPR, TEM and Raman spectroscopy. XRD analysis showed that all the support oxides chiefly contained tetragonal zirconia and minor monoclinic ZrO2 together with WO3 phases. With Raman spectroscopy, the surface structure of WO3 (800 cm-1 for W-O bond, 268 cm-1 for W-O-W bonds, and 711 cm-1 for W=O bond) and the monoclinic and tetragonal ZrO2 phases were observed. In situ FTIR spectra confirm that both Lewis and Brönsted acid sites were presented in the catalysts surface. In the hydroisomerization of n-heptane, the highest n-heptane conversion (60.8%) was obtained over 1 wt% Pd/WO3-ZrO2 with 25 wt% WO3 at 300 °C with selectivity around 90%. Various C7 isomers products were detected. Their yields were dependent of the reaction temperature and varied with WO3 concentration. In the monobranched isomers, 2-methylhexane was dominant; while, in the multibranched isomers, 2,3- dimethylpentane was the main component.